1. Field of the Invention
The present invention relates to a communication buzzer, and more particularly, the present invention relates to a communication buzzer which is used in a communication device such as a portable phone, a beeper or the like, to inform of the reception of an incoming call.
2. Description of the Related Art
Generally, a direct current buzzer used in a small-sized communication device functions to inform of the reception of an incoming call The direct current buzzer serves as an essential component of a communication device such as a portable phone, a beeper or the like. Recently, as communication devices continue the trend toward structural miniaturization in view of portability or convenience for use, components thereof have also been gradually miniaturized.
Referring to FIG. 1, there is shown a cross-sectional view which illustrates a structure of a communication buzzer according to the related art. The direct current communication buzzer 11 includes a printed circuit board (PCB) 2 which has a lead wire 1. A base plate 3 is put onto an upper surface of the printed circuit board 2. A shaft 4 is mounted to a center portion of the printed circuit board 2 and base plate 3 such that it projects upward through them. Electromagnetic actuating means 5 is fitted around the shaft 4 which projects upward. As an example, a core prepared by winding a coil around an iron-core is used as the electromagnetic actuating means 5. Both ends of the electromagnetic actuating means 5 are connected to positive and negative electrodes of the printed circuit board 2, respectively, by means of soldering, etc.
On an upper surface of the base plate 3, a magnetic piece 6 is disposed around the electromagnetic actuating means 5 such that it is separated therefrom by a predetermined radial distance. Also, a vibrating plate support member 7 having a cylindrical configuration is arranged on an edge portion of the base plate 3 such that it surrounds the magnetic piece 6. A vibrating plate 8 is seated onto a shoulder which is formed adjacent an upper end of a circumferential inner surface of the vibrating plate support member 7. Finally, an outer case 9 is fitted around the vibrating plate support member 7 such that it closes an upper end thereof, and a packing material is filled into a gap between the vibrating plate support member 7 and the printed circuit board 2 thereby to construct a complete communication buzzer 11.
In the communication buzzer 11 constructed as mentioned above, as the vibrating plate 8 is vibrated, a sound wave is generated as described below. First, magnetic force generated by the magnetic piece 6 is absorbed by the base plate 3 which is made of metallic material, and then, is transferred to the shaft 4. The shaft 4 which receives the magnetic force through the base plate 3, attracts and curves the vibrating plate 8 downward. In this state, as current is applied to the printed circuit board 2 through the lead wire 1, the shaft 4 is magnetized through the electromagnetic actuating means 5 to further attract and curve the vibrating plate 8 downward. Thereafter, as the current applied to the printed circuit board 2 is momentarily shut off, the vibrating plate 8 which is attracted and curved downward, is returned to its original curved position.
Accordingly, by repeatedly and alternately performing a current supply operation and a current shut-off operation, the vibrating plate 8 is vibrated while being further curved downward and being returned to its original curved position, thereby generating a sound wave.
However, the communication buzzer 11 of the related art suffers from defects in that since the current supplied to the electromagnetic actuating means 5 can leak through the conductive base plate 3, the separate printed circuit board 2 must be necessarily used, and by this, manufacturing cost is increased and assembling time for assembling the printed circuit board 2 and the base plate 3 is lengthened.
In particular, due to the fact that the communication buzzer 11 of the related art has a number of components, assembling time is further lengthened and miniaturization of an end product is considered to be difficult. That is, in order to miniaturize a communication buzzer and shorten assembling time, sizes of components must be decreased and the whole structure of the communication buzzer must be simplified. Nevertheless, in the communication buzzer 11 of the related art, since the printed circuit board 2 and the base plate 3 are assembled with each other, the shaft 4 is mounted to the printed circuit board 2 and the base plate 3, the electromagnetic actuating means 5 and the magnetic piece 6 are disposed on the upper surface of the base plate 3 such that they are spaced apart from each other by the predetermined radial distance, and the vibrating plate support member 7 for arranging the vibrating plate 8 is separately fabricated and fitted around the magnetic piece 6, the number of components is increased and assembling procedure is complicated, thereby lengthening assembling time and setting limits to the miniaturization of the components.
Moreover, when the radial distance between the electromagnetic actuating means 5 and the magnetic piece 6 does not kept constant, the vibrating plate support member 7 is apt to be deviated from a center of the shaft 4. If the vibrating plate support member 7 is deviated, because the vibrating plate 8 is also deviated from the center of the shaft 4, reliable operation of the vibrating plate 8 cannot be ensured. Therefore, assembling operation of the communication buzzer must be carefully performed, by which assembling time is further lengthened and productivity is deteriorated.
In addition, while a distance between an upper end of the shaft 4 and the vibrating plate 8 should be kept constant, in the communication buzzer of the related art, since the shaft 4 is mounted to the printed circuit board 2 and the base plate 3 by being squeezed against them through a press, an assembling error may be caused. Accordingly, a constant distance between the upper end of the shaft 4 and the vibrating plate 8 cannot be ensured.